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Milk used to be simple. Your mom went to the store, bought a carton, and then plunked down a tall glass right next to your chocolate chip cookies. Nowadays, Mom might find the choices downright bewildering: lactose-free milk, nondairy beverages such as soy, rice, and almond milks -- even oat, multigrain, or hemp milk.

These alternatives have hit the store shelves, but why choose them? The reasons are many. Some people buy lactose-free milk because uncomfortable symptoms of lactose intolerance have soured them on regular cow’s milk. Others, such as people with true milk allergies, can’t drink cow’s milk at all, so they turn to plant-based milks to get their nutrition.

Cow’s milk, including lactose-free cow's milk, does offer strong benefits, says registered dietitian Karen Ansel, MS, RD, CDN, a spokeswoman for the American Dietetic Association and co-author of the Baby and Toddler Cookbook. “In addition to having a lot of calcium and vitamin D -- which are really important and we don’t get enough of -- cow’s milk is a really great source of protein.”

Lactose Intolerance

Lactose intolerance occurs when you don’t make enough of an enzyme called lactase, which breaks down the milk sugar lactose, Ansel says. When the sugar stays undigested, telltale signs can creep up: diarrhea, gas, and bloating.

“You can have varying degrees of lactose intolerance,” Ansel says. “Somebody might be able to actually drink a glass of milk in a day. Somebody might not be able to have any. Somebody might be able to have some if they space it out, so it really depends. Different people might produce different amounts of lactase.”

“As we get older, we produce less and less of it,” she says. “What a lot of people find is that in adulthood, it becomes more of a problem, but it wasn’t a problem for them when they were children.”

Experiment to see how much dairy you can tolerate, or eat food when you drink regular milk to try to ease symptoms, Ansel says. You can also buy lactose-free cow's milk, which has been treated with lactase so that the milk sugar is completely broken down, she says. Nutritionally, lactose-free cow's milk is comparable to regular cow’s milk, she says. Or you can try other lactose-free milk options.

But one word of caution, Ansel says. Some people believe that they’re lactose intolerant when they actually have a true milk allergy. “There’s actually a pretty big difference,” she says. “Lactose intolerance has to do with an inability to metabolize or break down lactose. That’s a metabolic issue.” And a true milk allergy is uncommon.

In contrast, “A food allergy to milk has to do with your immune system. When you drink milk, your body perceives one of the proteins in milk as a foreign invader. Your body responds by producing antibodies to fight that protein. When those antibodies are released, it causes the symptoms of an allergic reaction.”

Milk allergy symptoms can include itching, swelling, hives, a runny nose, or difficulty breathing, Ansel says. Also, “You could have digestive symptoms. That’s why a lot of times, people confuse milk allergy with lactose intolerance. They do sometimes have overlapping symptoms.”

“Allergy can be a dangerous thing,” she adds. If you suspect that you might be allergic to milk, ask your doctor about allergy testing, she says. “You really shouldn’t try to diagnose it yourself.”

Nondairy Alternatives

For people who have lactose intolerance, nondairy beverages offer another alternative, experts say. These plant-based "milks" also appeal to vegetarians and vegans.

“There’s a lot of variety, which is great,” Ansel says.

Oat, multigrain, potato, and hemp milk are on the market. But the old standbys -- soy, almond, and rice milk -- are by far the most common ones that people use for drinking or cooking, says registered dietitian Suzanne Havala Hobbs, DrPH, MS, RD. Hobbs is a faculty member in the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill. Hobbs also wrote the book Living Dairy-Free for Dummies.

The nondairy milks vary in taste and consistency. For example, soy milk has a thicker consistency than cow’s milk, while rice milk is thinner. Furthermore, rice milk is a popular choice, Hobbs says, because “rice milk looks bright white, just like cow’s milk.” In contrast, almond and soy milk have a slightly beige color. Almond milk also has a faint almond taste.

Comparing Nutrition

When choosing a beverage, be aware that the various types differ in key areas of nutrition, Ansel and Hobbs say.

Lactose-free cow’s milk is high in calcium and other nutrients and often fortified with vitamin D, like regular cow's milk. If you choose a nondairy alternative, it’s smart to compare a nondairy milk’s food label to that of cow’s milk to make sure that you’re getting similar levels of fortification, nutrients, and protein, Ansel says. “If you really don’t like milk, and you’re not going to drink milk, these are a good way -- as long as they’re fortified -- to get calcium and vitamin D,” she says.

A quick rundown on how nondairy milks compare to cow’s milk in key areas:

Calcium, Vitamin D, and Vitamin B12

“Calcium and vitamin D are biggies because some of these milks will be fortified with them, and others won’t, so you really need to read the label,” Ansel says. Even when nondairy milks are calcium-fortified, levels may vary from product to product.

Ansel also suggests that people check the ingredient list for the type of calcium added. For example, soy milk that is fortified with calcium carbonate is well-absorbed, she says, “but if it’s fortified with tricalcium phosphate, then it may not be as well-absorbed.”

In contrast, almond milk has 1 gram of protein per cup, while rice milk contains only 0.28 grams to 1 gram, Anding says.

Another big plus with soy milk: it offers complete protein, just as cow’s milk does. What does that mean? “It has all the essential amino acids that your body cannot make, so you have to get them through food,” Ansel says. “That’s really the best quality protein. Those are usually found in animal foods, but there are a few small exceptions and soybeans are one of them,” she says.

Hobbs also considers soy milk a strong choice. “It’s highly nutritious, especially fortified soy milk. It’s very similar to cow’s milk in its nutritional profile. It’s a very good alternative to cow’s milk,” she says.

Cholesterol and Saturated Fat

Whole and low-fat cow’s milk contains cholesterol and saturated fat, although people can cut back by choosing skim or fat-free milk. In comparison, soy, rice, and almond milk contain no cholesterol because they’re plant-based.

Besides using nondairy options for drinking, stirring into coffee, and pouring onto cereal, you can substitute them for cow’s milk in recipes, Hobbs says. She has used soy, almond, and rice milk in smoothies, nondairy ice cream, mashed potatoes, soups, sauces, and other dishes.

Some cooking tips:

In a recipe, substitute lactose-free cow's milk or a nondairy alternative, cup for cup, in place of regular cow’s milk. Soy milk is versatile and can be used in almost any recipe, Hobbs says. In contrast, rice milk’s thinner consistency doesn’t lend itself well to sauces or puddings, she says. “Those dishes don’t come out as creamy. It’s sort of the difference between using whole milk and skim milk.”

Nondairy beverages, such as soy and almond milk, come in plain varieties as well as vanilla, chocolate, and other flavors. Use plain varieties for savory recipes, such as mashed potatoes, cream sauces, cream soups, scrambled eggs, or omelets, Hobbs says. Save the vanilla, chocolate, and other flavored milks for sweet foods, such as cookies, cakes, quick breads, muffins, pancakes, and waffles. If you want to keep only one type of nondairy beverage on hand, for example, soy milk, choose the plain type because it works with both savory and sweet recipes.

If a recipe calls for buttermilk, make your own by adding 2 teaspoons of vinegar or lemon juice to one cup of any nondairy milk. Mix well and let it stand for a few minutes before using.

Don’t store nondairy milks in the freezer, Hobbs says. Doing so won’t affect the product’s safety or nutrition, but freezing will harm consistency.